Baddeleyite

Baddeleyite
Baddeleyite from Phalaborwa, South Africa
General
CategoryOxide mineral
Formula
(repeating unit)
Zirconium dioxide (ZrO2)
IMA symbolBdy[1]
Strunz classification4.DE.35
Dana classification04.04.14.01
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupP21/c
Unit cella = 5.1505 Å,
b = 5.2116 Å,
c = 5.3173 Å, β = 99.23°; Z = 4
Identification
ColorColorless to yellow, blue, green, greenish or reddish brown, brown, iron-black
Crystal habitTabular prismatic, radially fibrous in botryoidal masses
TwinningUbiquitous polysynthetic on {100} and {110}
Cleavage{001} distinct
FractureIrregular uneven to subconchoidal
TenacityBrittle
Mohs scale hardness6.5
LusterGreasy to vitreous
StreakWhite
DiaphaneityTransparent to translucent
Specific gravity5.5–6
Optical propertiesBiaxial (–)
Refractive indexnα = 2.130
nβ = 2.190
nγ = 2.200
Birefringenceδ = 0.070
PleochroismX = yellow, reddish brown, oil-green; Y = oil-green, reddish brown; Z = brown, light brown
2V angleMeasured: 30° to 31°
Dispersionr > v, rather strong
Other characteristicsBlue-green cathodoluminescence
References[2][3][4]

Baddeleyite is a rare zirconium oxide mineral (ZrO2 or zirconia), occurring in a variety of monoclinic prismatic crystal forms. It is transparent to translucent, has high indices of refraction, and ranges from colorless to yellow, green, and dark brown. See etymology below.

Baddeleyite is a refractory mineral, with a melting point of 2700 °C. Hafnium is a substituting impurity and may be present in quantities ranging from 0.1 to several percent.

It can be found in igneous rocks containing potassium feldspar and plagioclase. Baddeleyite is commonly not found with zircon (ZrSiO4), because it forms in silica-undersaturated rocks, such as mafic rocks. This is because, when silica is free in the system (silica-saturated/oversaturated), zircon is the dominating phase, not baddeleyite. It belongs to the monoclinic-prismatic class, of the P21/c crystal system. It has been used for geochronology.[5]

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C., eds. (1990). "Baddeleyite". Handbook of Mineralogy (PDF). Vol. III (Halides, Hydroxides, Oxides). Chantilly, VA, US: Mineralogical Society of America. ISBN 0962209724. Retrieved December 5, 2011.
  3. ^ Baddeleyite. Webmineral
  4. ^ Baddeleyite. Mindat
  5. ^ Bayanova, T.B. (2006). "Baddeleyite: A promising geochronometer for alkaline and basic magmatism". Petrology. 14 (2): 187–200. Bibcode:2006Petro..14..187B. doi:10.1134/S0869591106020032. S2CID 129079168.